[X-Unix] Manual launch of a timed launchd task?

[Jeff Porten]

I've got several tasks set up to go off at 3 AM on a server I'm using  
(Tiger Server).  Working from the command line, so I manually put the  
files in /Library/LaunchDaemons and loaded them.

What I'd like to do is fire them up now and see if they work.  But  
when I do launchctl start, nothing happens -- I presume that the 3 AM  
launch is overriding the start command.  How do I tell these to fire  
immediately?

Corollary question: I have two tasks loaded that I can't unload  
because the files no longer exist.  I'd rather not reboot the  
server.  How do I drop these from the job list?  I noticed the  
shutdown command, but I don't want to unload the System tasks.

Thanks,
Jeff